Ethylene (co)Oligomerization by Phosphine‐Pyridine Based Palladium and Nickel Catalysts

Abstract

Phosphine and pyridine groups have been widely employed in various olefin polymerization catalysts. In this contribution, these two moieties are connected using different bridges, and the properties of their corresponding palladium and nickel complexes are investigated. A series of CH2, NH and O bridged phosphine‐pyridine ligands (2‐(diarylphosphino)methyl‐pyridine, 2‐(diarylphosphino)amino‐pyridine, 2‐diarylphosphinito‐pyridine) are synthesized and characterized. For the CH2 bridged ligand, the introduction of a C6F5 substituent leads to the generation of a mixture of diastereomers, which can be separated by column chromatography. Starting with these five phosphine‐pyridine ligands, the corresponding palladium and nickel complexes are prepared and characterized. The bridging moiety (CH2, NH and O), the substituents on the bridge, and the ligand orientations significantly influence the properties of the metal complexes in ethylene oligomerization and cooligomerization reactions. For the palladium complexes, ethylene oligomerization and cooligomerization with some polar comonomers (methyl acrylate, butyl vinyl ether, vinyltrimethoxysilane, allyl acetate and allyl choride) can be realized. For the nickel complexes, ethylene oligomerization followed by Friedel‐Crafts addition of the resulting oligomers to toluene solvent leads to the formation of branched alkylated aromatic materials.

Bulky iminophosphine‐based nickel and palladium catalysts bearing 2,6‐dibenzhydryl groups for ethylene oligo‐/polymerization

“…reported some cationic iminophosphine‐based Ni catalysts C for ethylene polymerization to produce branched PEs with higher molecular weights . The ethylene oligomerization activity was greatly decreased along with chelate‐ring size reduction in a series of pyridine‐phosphine Ni complexes D and E . However, there are only a small number of the iminophosphine‐based Ni and Pd catalysts have been examined in olefin oligo‐/polymerization reaction studies .…”

Catalytic behavior tuning via structural modifications of silylated‐diphosphine Ni(II) complexes for ethylene selective dimerization

“…[14] Furthermore, nickel complexes based on phosphine and pyridine ligands when activated with tetrakis(3,5-bis (trifluoromethyl)phenyl)borate (NaBAF) afforded considerable activity for ethylene oligomerization and polymerization. [15] Moreover, the nickel complexes of amidine/phosphine oxide and α-iminoketone ligands exhibited high thermal stability and considerable catalytic activity toward homopolymerization and copolymerization even in the absence of cocatalyst. [16,17] Similarly, tridentate pyrazolyl-based nickel complexes on activation with Methylaluminoxane (MAO) in toluene offered high dimerization activity and excellent C 4 selectivity.…”

Extremely Active Ethylene Tetramerization Catalyst Avoiding the Use of Methylaluminoxane: [iPrN{P(C6H4‐p‐SiR3)2}2CrCl2]+[B(C6F5)4]−

“…Catalyst development for ethylene oligomerization is an ongoing research topic in both academia and industry. [29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45] 4 ] À (2.0 eq), CrCl 3 (THF) 3 , and PNP ligand that exhibited high activity (up to 4000 kg/g-Cr/h) when combined with common and inexpensive alkylaluminum iBu 3 Al (Scheme 1). [46] We presumed that the chloride-bridged adduct (i. e., [(PNP)Cr(Cl)(THF)(μ 2 -Cl) 2 Al(acac)] 2 + [B(C 6 F 5 ) 4 ] À 2 ) might be formed between the cationic Cr species [(PNP)CrCl 2 ] + [B(C 6 F 5 ) 4 ] À and the cationic Al species [ClAl(acac)] + [B(C 6 F 5 ) 4 ] À .…”

“…In this study, we developed an extremely active catalytic system that eliminates the issues associated with the original Sasol system. Catalyst development for ethylene oligomerization is an ongoing research topic in both academia and industry …”